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It’s pretty common to see big 4WD’s driven daily on the road. Bigger tyres and lift kits will make a 4WD more capable off-road, but it also makes them illegal on the road, unless you have jumped through a number of hoops. A vehicle that is illegal has a number of very serious risks attached to the driver, which we will go into below.


For starters, let’s consider what is legal, and then you will know where you stand right now. In WA, VSB 14 has been adopted, which is a document that goes through the large majority of modifications done to vehicles, and what is legal or illegal.

If you have modified any of the following items on your 4WD it would be a very good idea to do some reading up:

  • Tyre size
  • Suspension
  • Wheel track
  • Brakes
  • Body
  • Chassis
  • A vehicle that could be over weight


In VSB 14, It states that your roof height may only be lifted by 2” (or 50mm) from the factory (or standard height) before it needs to go through a lane change test. This 50mm is the total combination of body lifts, suspension lifts and bigger tyres.  Currently NO Vehicle over 3″ may have a lane change test.  Therefore 3″ lift is the biggest lift in W.A.

You are also not allowed to fit tyres that are more than 50mm bigger than the factory tyre diameter. For a lot of four wheel drives, 31’s are standard tyres, so 33’s are the biggest you can legally fit (or 285’s from 265’s).

In reality then, you are limited to:

1” lift and 2” bigger diameter tyres (together)

2” lift and the same size tyres.

For those of you out there that are running bigger than a 2” lift, your vehicle is illegal. If you have bigger tyres than standard and a 2 inch lift (or bigger), your vehicle is also illegal. The only way this does not apply is if it has been signed off by an engineer.

For more information regarding VSB14 click on or paste the link below to your browser



Lowering of vehicles

The road clearance of a fully laden vehicle must not be less than 100mm measured at any part of the vehicle other than the wheel rim or brake backing plates.

(This does not apply where a lesser clearance has been specified by the manufacturer.)

When lowering or raising a vehicle body (front or rear), the following additional restrictions are based on the manufacturer’s dimensions for the standard unmodified vehicle while unladen:

  • The ride height measured between the rubber bump stop and the corresponding metal stop may be reduced by no more than one third.
  • The rebound travel measured between the rubber rebound stop and the corresponding metal stop (or the extension of the shock absorber for vehicles without a rebound stop) may be reduced by no more than one third.
  • Coil springs are to remain in locating seats on full suspension droop without forcibly being removed.

In addition, the normal relationship between the front and rear suspension heights must not be unduly affected. Replacement springs (shorter or taller) must have the same or greater load capacity as the original springs.

Suspension coil springs must not be shortened by cutting or heating.

Leaf spring suspensions must not be raised by the use of extended shackles, adjustable metal plates or by placing the leaf springs to the opposite side of the axle.

If lowering blocks are used, they must be either steel or aluminium.

Replacing some or all of the suspension system with an air or hydraulic suspension requires specific enginnering approval.


Airbags are designed to ASSIST with your leaf springs they are not designed to replace them!

What we mean is that manufacturers fit soft leaf springs as the end use of the vehicle may change once sold.  For example:

Brand new Navara Ute with factory well body.  A plumber buys the vehicle takes it to a body builder fits a canopy to it.  Then takes it home fills it with tools, fills it with pipe fittings, fills it with nuts and bolts and Gas bottles etc!

Nett result is this vehicle now has a constant load of 400 kilograms 24 hours a day and the rear of this vehicle is now sagged.  Whilst an airbag can lift this load the airbag has to be filled to such capacity that the chassis now sits predominantly on top of the airbag and not the springs leaves.  You can bend your chassis doing this!

Ideally the leaf packs need to be strengthened either by replacing them or resetting the existing leaves and adding in more leaves so that the spring leaves will now cope with the weight on top of them.

If this plumber pulls a trailer then you can fit airbags to assist with towing.

If you dont have too heavy a constant load then it may be possible to fit airbags but again to assist primarily with towing.

Always contact us for advice.  Its FREE


GVM (Gross Vehicle Mass)

GVM is the maximum weight that the vehicle or truck can carry, including its own weight, as measured where the tyres contact the road.

Kerb Weight

The kerb weight is the weight of the basic cab and chassis before any specific body has been added. It does however include an allowance for some fuel and lubricating oils, and may include the weight of a spare wheel and tyre.

Available Payload Capacity = GVM – kerb weight – tare weight

In normal life you will face more situations of towing a trailer, than when only driving a truck. The GVM is the total load the truck can carry on its own wheels, whereas GCM includes trailer weight.

GCM (Gross Combination Mass)

GCM is the total weight of the truck, trailer and their loads combined.

GCM = Weight of vehicle (truck) + equipment + weight of trailer + payload

The GCM on the ground should not exceed the manufacturer’s GCM rating, and trucks can not be loaded to exceed the truck’s GVM or individual axle capacities, even if the total combination weight is lower than the rated GCM.


We get asked this every day, probably every hour of every day?

The short answer is that the best lift kit is the most suited lift kit!

Suited means: What type of driving you intend to do, The kit has springs that are matched for the accessories you have on your vehicle, the vehicle has wheels that are also appropriately sized. You understand the mechanics of your components and the results they provide you.

Your bet answer will be to speak to us before you make up your mind!


Practically all 4wd’s are designed by vehicle manufacturers to carry some weight at some time.  Imagine buying a new vehicle only to find out that if you take some camping equipment away for a break or, you take some passengers on a trip with you that the vehicle steers so badly you are having to hang onto the steering wheel for dear life!  There must be a problem with it, the short answer?  Well yes there is!

There appears to be a decreasing trend by some customers, who ask us this question and they tell us they do not like to look of the stance of their 4wd?  Therefore they wish for their vehicle to be level!

If this is the case then please read on.

Manufacturers design vehicles with the rear of the vehicle up in the rear to allow for luggage, passengers, tools etc.  Ideally when laden, your vehicle must not be sagging down in the rear.  If it does then the effect will make your steering geometry out and you WILL notice that at higher speeds (40kph plus, and worse on highways) that you will end up having to really concentrate on your steering wheel as it will have a tendency to wander.  This is dangerous as you may not notice any hazards in the road.  We do not have to write about the after effects of this.  Our advice is, do not have a vehicle set to level.